At this time, GOP presidential rival Mitt Romney is the sole candidate granted protection.- Follow the Ticker on Twitter: @PoliticalTicker

A spokesman for the Secret Service declined to comment on the matter when contacted by CNN.

Meanwhile, a source with Newt Gingrich's campaign confirmed the former House speaker also requested protection. The source did not know when the paperwork was submitted but said discussions about putting in the request began last week.

Gingrich's campaign has not yet received a response from the Secret Service, the source said.